AC vs DC Heating in the Solar Corona: A Numerical Study of a Dated Dichotomy

The problem of explaining coronal heating has traditionally been framed in terms of a debate between impulsive, “DC,” heating mechanisms, involving current sheets and magnetic reconnection, and turbulent, wave-dissipative, “AC,” mechanisms. In a recent review however, Parnell and DeMoortel [Philo. Trans. Roy. Soc. A , 2012] argued that observations of the solar corona reveal a highly dynamical system in which it is likely that both “AC” and “DC” heating mechanisms play a role, and that it may be more sensible to ask what are the relative contributions of each type of mechanism. In this talk I will present a simple picture of the differences between these two classes of heating. I will also show for each case how one might infer predictions for how the rate of heating of a “loop" of coronal plasma should scale with the loop’s arc length. I will then show the results of a set of numerical simulations designed to test these scaling relations. Our results are consistent with the intuition that strong Alfvenic turbulent heating is dominant in loops whose arc lengths are large relative to their diameters. Nevertheless, we find that the scaling law that best matches our results over the entire range of arc lengths is a blend of the laws applicable at the extrema of the range of arc lengths. This outcome appears to be very much in the spirit of the views expressed by Parnell and DeMoortel, and thus appears also to indicate that further numerical studies designed to discriminate and quantify the contributions of each are in order.